Liquid fuel combustion device

ABSTRACT

Through a combination of A. THE SUPPLY OF OXYGEN SUBSTANTIALLY IN THE FORM OF PURE OXYGEN IN AN AMOUNT FAR LESS THAN THAT THEORETICALLY REQUIRED FOR COMBUSTION OF LIQUID FUEL TO BE BURNED IN SUCH A MANNER AS TO ATTAIN A VERY RAPID COMBUSTION TEMPERATURE RISE, B. WITH THE STRONG ACTIVATION OF THE LIQUID FUEL BY MIXING AND ATOMIZATION OF A PART OF THE FUEL LIQUID SUFFICIENTLY WITH THE OXYGEN, LIMITED IN QUANTITY, CLOSELY ADJACENT TO A LIQUID FUEL NOZZLE THEREBY TO FORM A HIGH-TEMPERATURE CENTER FLAME VERY CLOSE TO THE NOZZLE. C. A HIGH-TEMPERATURE FLAME HAVING A LARGE POTENTIAL HEAT PER UNIT VOLUME THEREOF, THAT IS, A FLAME OF EXTREMELY HIGH INTENSITY, IS OBTAINED EFFICIENTLY WITH A SMALL SUPPLY OF OXYGEN.

ilnited States Patent [191 Nakagawa et al. 1 ay 15, 1973 54 LIQUID FUEL COMBUSTION DEVHCE 1,151,496 8/1915 Pettis ..43l/DIG. 32 500,005 6/1893 Jones ...239/419.3 x

[ l Inventors: Masayoshl NakagaWa, N1ShmOm1Ya; l,07l,38l 8/1913 Anthony .239 429 x Toshihiro Hirai, Sak i; Yuji Suzuki, 2,290,785 7 1942 Turpin .239/430 x Amagasaki-shi; Ryozaburo Kimura; 2,484,272 10/1949 Crowe ...239/419.3 X

Masamichi Okahara, both of 1,396,086 8/I92l Anthony ..43 I/DIG. 32

Takarazuka, all of Japan [73] Assignee: Daido Sans Kabushiki Kaisha,

Osaka-shi, Minami-ku, Unagidani- Nakano-cho, Banchi, Japan 22 Filed: Mar. 29, 1971 [21] Appl. No.: 128,937

Related U.S. Application Data [62] Division of Ser. No. 794,221, Jan. 27, 1969, Pat. No.

[30] Foreign Application Priority Data Jan. 25, 1968 Japan ..43/47l2 Feb. 23, 1968, Japan ..43/1l674 Aug. 27, 1968 Japan ..43/74096 [52] U.S. Cl ..43l/10 [51] Int. Cl ..F23l 7/00 [58] Field of Search ..43l/2, 8, 349, 284,

431/10, DIG. 21, 22, 23, 32; 239/403, 405, 406, 419., 419.3, 422, 424.4, 428, 429, 430,

[ I References Cited I UNITED STATES PATENTS 3,275,057 9/1966 Ward ..43 I/284 802,297 10 1905 K'Lippers ..43 1 l8 FOREIGN PATENTS OR APPLICATIONS 952,673 3/1964 Great Britain ..43l/l0 Primary Examiner-Meyer Perlin Assistant ExaminerWilliam C. Anderson Attorney-Edwin E. Greigg [57] ABSTRACT Through a combination of a. the supply of oxygen substantially in the form of pure oxygen in an amount far less than that theoretically required for combustion of liquid fuel to be burned in such a manner as to attain a very rapid combustion temperature rise,

' b. with the strong activation of the liquid fuel by mixing and atomization of a part of the fuel liquid sufficiently with the oxygen, limited in quantity, closely adjacent to a liquid fuel nozzle thereby to form a high-temperature center flame very close to the nozzle.

0. a high-temperature flame having a large potential heat per unit volume thereof, that is, a flame of extremely high intensity, is obtained efficiently with a small supply of oxygen.

4 Claims, 5 Drawing Figures 1 LIQUID FUEL COMBUSTION DEVICE This application is a division of US. application Ser. No. 794,221, filed Jan. 27,1969, now US. Pat. No. 3,610,537 Masayoshi Nakagawa et al, inventors.

BACKGROUND OF THE INVENTION Combustion devices for burning liquid fuel by the addition of oxygen are required to minimize the issue and consumption of expensive oxygen gas for the combustion of the fuel, completely burn the liquid fuel issuing from the orifice and produce a high-temperature, intense flame (with a high calorific value per unit volume of the flame).

In conventional devices of the type described, the combustion efficiency and flame temperature can be increased by oxygen enrichment (i.e., by the addition of oxygen gas to air in order to bring a corresponding decrease of the amount or proportion of nitrogen in the air which takes part in the combustion). However, the combustion efficiency depends largely upon the manner in which the enrichment is made.

For example, some devices are so designed that oxygen gas is passed into the central part of the flame and, because the oxygen gas and liquid fuel are separately supplied without being pre-mixed, the increase of the nozzle velocity of oxygen gas above a certain value produces a jet of oxygen gas fast enough to blow the merging or mixing point of the gas and liquid fuel away from the nozzle tip. Consequently, oxygen gas and liquid fuel cannot be diffused and mixed thoroughly and rapidly notwithstanding the addition of oxygen gas. The arrangement is thus disadvantageous in that the oxygen gas fed in is only partly utilized and the flame thus obtained is not of a sufficiently elevated temperature.

As described above, it has hitherto been in practice to atomize liquid fuel beforehand and allow the atomized fuel to issue from an orifice in such a way as to simply entrain oxygen gas and carry it into the flame. Efforts have thus been centered on direct promotion of the combustion of the main flame through the addition of or enrichment with oxygen. Here it may appear at a first glance that the pre-atomization of liquid fuel will produce a high-temperature, high-intensity flame, but in reality the practice is merely contributory to complete combustion of liquid fuel. By the complete atomization the liquid fuelis widely diffused in the space, and the flame produced by combustion of this difiused liquid fuel is so thick and long that the calorific value per unit volume is below the level otherwise attained with the same quantity of heat, and the flame intensity is accordingly decreased. The flame of very large size also causes dissipation of heat over a wide area with a consequent drop of the flame temperature.

As will be appreciated from the foregoing, there has been no method and device for effecting the combustion of liquid fuel with a high flame intensity by the mere addition of a very small amount of pure oxygen.

This invention is directed to the provision of a liquid fuel combustion device which can satisfy all of the requirements above mentioned.

According to the present invention, the aforementioned disadvantages of the conventional devices are eliminated in the following way. First, a part of liquid fuel is burned with pure oxygen in an amount of. less than the chemical equivalent in the central part of the nozzle tip of the combustion device to effect the combustion in an entirely pure oxygen atmosphere so as to produce a high-temperature, stable center flame there. The remainder of liquid fuel is then ejected through nozzle means so as to envelop the center flame and is instantaneously vaporized and decomposed by the extremely high heat of reaction of the center flame to produce, at the same time, a large amount of active radicals which rapidly diffuse in air serving to form a main flame. Altogether, a high-temperature flame of extremely great intensity is thus obtained. In other words, the combustion system of the invention is characterized in that the flame thereby produced includes a center flame and a main flame and that the pure oxygen added is not directly consumed for the combustion of the entire flame but it serves to form a center flame of an ultra-high temperature by the combustion of fuel in a totally pure oxygen atmosphere and then indirectly promotes the burning of the main flame with the aid of the center flame.

SUMMARY OF THE INVENTION The liquid fuel combustion device according to the present invention pertains to a liquid fuel burner.

The device of the invention is characterized by a method and arrangement as represented by the first embodiment thereof shown in FIG. 1, wherein an oxygen nozzle and a liquid fuel nozzle are separately provided in the central part of the combustion device, surrounded by a line for air or steam or their mixture, and a mixing chamber is provided near the tip of the oxygen nozzle in which a part of the liquid fuel is mixed with oxygen gas.

In this way it is made possible, in mixing and burning the liquid fuel with oxygen gas, to feed a part of the liquid fuel into the mixing chamber thereby to atomize, mix and burn the part of liquid fuel in that chamber, and also effect almost complete volatilization and decomposition of the rest of liquid fuel by the heat of reaction due to the partial combustion so that a flame as a whole at a high temperature and having a great intensity and stability can be produced.

As is well known, active radicals have important bearings upon the promotion of combustion. In accordance with the present invention, the active radicals are produced in a large quantity as the remainder or most of the liquid fuel is volatilized and decomposed around the stabilized center flame by the heat of reaction (i.e., the heat of combustion) of the center flame. This production of active radicals is combined with the transfer of heat from the high-temperature center flame that exists very close to the nozzle tip to promote the combustion of the main flame (i.e., the flame formed by the combustion of most of the liquid fuel in mixture with air or the like supplied through the gas line).

Thus, the combustion of a part of liquid fuel atomized and mixed with oxygen in the mixing chamber produces a small, highly-stable center flame at a high temperature at the nozzle tip, and the heat of reaction of the center flame in turn volatilizes and decomposes most of the liquid fuel to form a main flame around the center flame and very close thereto by the combustion upon diffusion with air or the like. Thus, a flame as a whole which is short in length can be obtained. By shortening the overall flame length in this way, the flame temperature can be raised and the quantity of heat per unit volume of the flame can be increased so as to heighten the flame intensity.

It is thus to be understood that the amount of pure oxygen that issues from the oxygen nozzle is controlled to a range (2 to percent) that is far less than the theoretical amount of oxygen required for the combustion of the liquid fuel.

It is thus only necessary to supply from 2 to 15 percent of pure oxygen on the basis of the theoretical oxygen requirement in order to obtain a flame of high intensity.

In a further embodiment of the invention shown in FIG. 4, the oxygen nozzle is disposed inside the liquid fuel nozzle coaxially or substantially coaxially therewith, and an orifice portion for abruptly changing the pressure of oxygen gas thereby to cause a sudden increase of the oxygen flow velocity is formed in the central portion of the oxygen gas passage inside the oxygen nozzle away from the opening at the tip of the nozzle and at a point upstream of the flow direction of the oxygen gas, and a flow passage or passages branched from the liquid fuel nozzle are open in the oxygen nozzle at a point between the orifice portion and front end of the oxygen nozzle.

The orifice portion produces vortices of oxygen wherein a part of the liquid fuel is mixed. As a result, the mixing of the liquid fuel and oxygen gas is promoted and the ignitability is much improved and further a stabilized center flame is thereby formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows in longitudinal cross section the essential part of the first embodiment of the liquid fuel combustion device of the present invention;

FIG. 2 is an enlarged longitudinal cross section of the oxygen nozzle shown in FIG. 1;

FIG. 3 is an elevational view explanatory of the pattern of flame according to the first embodiment;

FIG. 4 shows in cross section a further embodiment of the invention disclosed in FIG. 1 and;

FIG. 5 is an enlarged longitudinal section of the oxygen nozzle of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the liquid fuel combustion device according to the present invention will now be described in conjunction with FIG. 1 showing the first embodiment thereof. In the center of the device shown there is provided an oxygen line 51 to the front end of which is fitted an oxygen nozzle 52. The two members are connected to each other through the engagement of threaded portions 53 detachably to the axis of the oxygen line 51. This detachability of the oxygen nozzle 52 permits selective use of a plurality of interchangeable oxygen nozzles 52. Through the oxygen line 51 and oxygen nozzle 52 high purity oxygen gas passes usually under a low pressure of about 0.3 to 2.0 kg/cmG and is emitted from the tip 54 of the oxygen nozzle 52.

Oxygen line 51 is surrounded by a liquid fuel line 56, to the front end of which is also fitted a liquid fuel nozzle 58 as if to envelop the oxygen nozzle 52. This liquid fuel nozzle 58 is connected through the engagement of threaded portions 57 to the liquid fuel line 56 in such a manner that it can be detached therefrom. The detachability of this liquid fuel nozzle 58 serves the same purposes as those of the oxygen nozzle 52 already described. Through the liquid fuel line 56 and liquid fuel nozzle 58 flows a liquid fuel such as a heavy oil.

Liquid fuel line 56 is further surrounded by a gas line 59 which is connected at the front end with a gas nozzle 61 enveloping the liquid fuel nozzle 58, detachably from the line through the engagement of threaded portions 60. The detachability of this gas nozzle 61 permits the same functions as those of the oxygen nozzle 52 and liquid fuel nozzle 58. Through the gas line 59 and gas nozzle 61 and via another line 67 passes air or steam or their mixture for atomizing the heavy oil. This gas for atomization use need not always be kept at a high pressure or run at a high velocity. Therefore, the feed arrangement may be of a relatively simple structure. Displacement of the nozzles with respect to one another enables the supply of gas to be shut off or adjusted where necessary.

Near the tip 54 of the oxygen nozzle 52 there is formed a mixing chamber wherein a part of the heavy oil is mixed with oxygen gas. As shown in an enlarged longitudinal section in FIG. 2, the oxygen nozzle 52 is formed with one or a plurality of passages 62 for the introduction of the heavy oil that are open in the bore of the nozzle 52 close to the tip 54. Thus, a mixing chamber 63 is defined which attracts a part of the heavy oil into the oxygen nozzle 52 by the injector action of the apertures under the influence of the flow of oxygen gas through the oxygen nozzle 52 at a flow rate within a certain range, and thus mixes the heavy oil so attracted by suction with the oxygen gas.

With the construction above described, the burner 64 is accommodated in a combustion-sustaining air line 69 coaxially or substantially coaxially therewith, usually penetrating altogether through a furnace wall 68 with the front end portion held inside the furnace.

Oxygen gas that flows through the oxygen nozzle 52 issues from the tip 54 past the mixing chamber 63. As it passes along the heavy oil-introduced passages 62, it induces an injector action thereby to attract by suction a part of the heavy oil in the liquid fuel nozzle 58 through the passages 62 into the oxygen nozzle 52. The fraction of heavy oil thus attracted is atomized and mixed up by the oxygen gas passing through the mixing chamber 63 and in the atomized and mixed state it is thus blown out of the tip 54. As shown in FIG. 3, this atomized mixture upon ignition forms a hightemperature and well-stabilized center flame 65 due to combustion with pure oxygen gas adjacent to the tip center of the burner 64.

The remainder of the heavy oil is emitted from the tip of the liquid fuel nozzle 58 into the atmosphere along the periphery of the center flame 65. At this time, the heavy oil is atomized and dispersed by the gas also issuing out of the gas nozzle 61 surrounding the liquid fuel nozzle 58. The liquid fuel thus atomized and dispersed is vaporized and decomposed around the center flame 65 by the high heat of reaction thereof and gives off a large amount of active radicals. The increased volume of active radicals combines with the high heat of reaction of the center flame 65 to promote the combustion of most of the liquid fuel so vaporized and decomposed. Around the center flame 65 and at a point quite close thereto, the vaporized and decomposed liquid fuel is burned in a state diffused by and mixed with the combustion air supplied from the combustionsustaining air line 69, thus forming a main flame 66. On

account of the high temperature of the center flame 65, the mixing of the atomized liquid fuel after vaporization with oxygen in the surrounding air is rapidly accomplished due to the high molecular velocity. In this manner the gaseous mixture is burned at a high burning velocity.

Accordingly, the main flame 66 having the hightemperature center flame 65 at the tip of the burner 64 is so formed that the main flame 66 itself has a short overall length. The quantity of heat being the same, the short main flame 66 has a higher calorific value per unit volume than ordinary flames, and hence a greater flame intensity. Because the flame is short and the surface area is small, the heat-radiating area is accordingly limited and the heat of combustion can be supplied to a desired zone concentrically and efficiently without waste. Further, because the flame length is short and the main flame 66 is formed near the burner 64, flame stability is attained without the possibility of lifting.

Combustion-sustaining air need not always be supplied through the air line 69 as illustrated in this embodiment, but it may be introduced from a separate route. In any case, it is most desirable that the air be fed in the direction toward the tip of the burner 64 or around the center flame 65.

For the reasons above stated, it is possible according to the present invention that through a combination of a. the supply of oxygen substantially in the form of pure oxygen in an amount far less than that theoretically required for combustion of liquid fuel to be burned so that a very rapid combustion temper ature rise can be attained,

. with the strong activation of the liquid fuel by mixing and atomization of a part of the fuel liquid sufficiently with the oxygen, limited in quantity, closely adjacent to a liquid fuel nozzle thereby to form a center flame at a suitable temperature very close to the nozzle,

0. a high-temperature flame having a large calorific value per unit volume thereof, that is, a flame of extremely high intensity, is obtained efficiently with a small supply of oxygen.

It is further to be noted that the nozzles are fitted to be adjustable relative to one another in the longitudinal direction by means of adjustment setting of the respective regulating handle (not shown in the drawings). This adjustment, together with readjustment of the respective fluid pressure, enables a single type of nozzle to meet any material changes in the amount of fuel oil and oxygen to be added, and permits adjustments of flame contour over an extensive range.

The construction of the additional embodiment will now be explained described.

To an oxygen line 145 disposed in the central part of the device is connected an oxygen nozzle 152 through a nozzle joint. Surrounding this oxygen line 145 there is provided a liquid fuel line 147, to the front end of which is connected a liquid fuel nozzle 158. The liquid fuel line 147 and liquid fuel nozzle 158 are arranged outside the oxygen line 145 and oxygen nozzle 152 coaxially or substantially coaxially therewith. Further outside the liquid fuel line 147 an air line 148 is disposed which has an air nozzle 149 at its front end. In the middle part of the oxygen gas passage 153 in the oxygen nozzle.152 there is formed an orifice 155 integrally with the oxygen nozzle 152 and which protrudes axially at a point fairly upstream of the oxygen flow direction from the tip 154 of the nozzle 152 and in the direction approaching the center of the oxygen flow passage 153 so that it can abruptly increase the flow velocity of oxygen gas. By the provision of this orifice 155 an abruptly changing portion is formed in the oxygen flow passage 153. In the space defined between the abruptly changing portion 150 and tip 154 of the oxygen nozzle 152 is provided one or a plurality of heavy oil passages 156 which are flow passages branched from the liquid fuel nozzle 158, inclined or substantially perpendicular to the axis of the device. Inside the oxygen flow passage 153 of the oxygen nozzle 152 there is formed a mixing chamber 157 between the orifice and tip 154.

A burner 161 of the foregoing construction is held in a combustion-sustaining air line 162 coaxially or substantially coaxially therewith, with the frontal part usually penetrating through a furnace wall 163 and extending into the furnace.

With such an arrangement, a part of the heavy oil is fed into the oxygen nozzle 152 through the passages 156 and mixed with. oxygen gas in the mixing chamber 157 and then the mixture is injected out of the tip 154 and burned to form a center flame 159. The remainder of the heavy oil is injected from the tip of the liquid fuel nozzle 158 and is atomized by the atomizing air issuing from the air nozzle 149 and is then burned together with the combustion-sustaining air supplied from the air line 162, whereby a main flame 165 is formed enveloping the center flame 159. This condition will be more fully described with reference to FIG. 5. The oxygen gas forced from the oxygen flow passage 153 toward the mixing chamber 157 is collected in the zone along the axial center of the oxygen flow passage 153 by means of the abruptly changing portion 150. The oxygen gas so collected is abruptly injected into the mixing chamber 157 along the axial center zone thereof. A part of the oxygen gas surrounding the outer periphery of the jet is abruptly introduced into the chamber where it is made turbulent in the mixing chamber 157 and caused to form a vortex flow therein. The heavy oil fed through the passages 156 is involved in the vortex of oxygen gas, and the oxygen gas and heavy oil in the vortex flow move toward the tip opening 154 while being thoroughly mixed and perfectly atomized in the mixing chamber 157 before the gaseous mixture issues from the tip 154.

Thus, the orifice 155 produces a fairly intense vortex flow and permits vigorous suction of liquid fuel through the passages 156 and very thorough dispersion and mixing of the liquid fuel with oxygen gas. The resulting mixture attains very good ignitability and flame stability within an extremely wide range of oxygen flow rate.

The advantage of this functional construction over the prior art is that the device of the construction according to the preferred embodiment is so modified in design as to supply pure oxygen in an amount of from 2 to 15 percent of the theoretical requirement. Therefore, the small volume of the flame is formed as above described, and the flame temperature is as high as about l700 to about 2,200 C, or the flame has a correspondingly high intensity.

What is claimed is:

1. A method of producing a flame from an oil burner, which has a high intensity and a high calorific value per unit volume comprising the steps of supplying high purity oxygen through a conduit to a introducing liquid fuel through a concentrically disposed conduit to a second nozzle;

diverting a portion of the liquid fuel in said other conduit into the first nozzle supplying the air to the burner;

mixing the air and the diverted portion of liquid in the nozzle and emitting therefrom a flame having a temperature ranging between about 1700C to about 2200C;

and furnishing gas through a second concentrically disposed conduit to a third nozzle to complete atomization and dispersion of the oil being emitted from the second nozzle by the flame ejected from the first nozzle.

2. A method of producing a flame from an oil burner as claimed in claim 1, further including the steps of emitting the oil and gas from their respective nozzles in a divergent direction and toward the flow line of the oxygen emitted from the first nozzle.

3. A method of producing a flame from an oil burner as claimed in claim 1, wherein the oxygen is under low pres-sure of about 0.3 to 2.0 kg/cm G.

4. A method of producing a flame from an oil burner as claimed in claim 1, wherein the oxygen is introduced to the first nozzle in an amount between 2-l5 percent of that theoretically required for combustion of the liquid fuel. 

1. A method of producing a flame from an oil burner, which has a high intensity and a high calorific value per unit volume comprising the steps of supplying high purity oxygen through a conduit to a first nozzle; introducing liquid fuel through a concentrically disposed conduit to a second nozzle; diverting a portion of the liquid fuel in said other conduit into the first nozzle supplying the air to the burner; mixing the air and the diverted portion of liquid in the nozzle and emitting therefrom a flame having a temperature ranging between about 1700*C to about 2200*C; and furnishing gas through a second concentrically disposed conduit to a third nozzle to complete atomization and dispersion of the oil being emitted from the second nozzle by the flame ejected from the first nozzle.
 2. A method of producing a flame from an oil burner as claimed in claim 1, further including the steps of emitting the oil and gas from their respective nozzles in a divergent direction and toward the flow line of the oxygen emitted from the first nozzle.
 3. A method of producing a flame from an oil burner as claimed in claim 1, wherein the oxygen is under low pres-sure of about 0.3 to 2.0 kg/cm2 G.
 4. A method of producing a flame from an oil burner as claimed in claim 1, wherein the oxygen is introduced to the first nozzle in an amount between 2-15 percent of that theoretically required for combustion of the liquid fuel. 